On Wed, Aug 12, 2026 at 08:12:03PM +0100, Mark Brown wrote: > In order to allow efficient implementation of GCS implementations are > permitted to do GCS specific caching, with barriers implicit in stack > switch operations
(GCSSS2) > and GCSB DSYNC as an explicit barrier. Since we do > not use GCS in the hypervisor or host kernel the hypervisor cannot rely > on any barriers being present in vCPU context switches other than those > it explicitly inserts. Add explicit barriers when loading and saving > vCPU state. > The same way we have a DSB, having a GCSB here seems required, as there may be pending GCS writes. Makes sense. Question: You state that we do _not_ use GCS in the hypervisor, nor in the host. I understand that we GCSB() when we exit the vcpu context, but why would we need to GCSB() before getting back in? If cpus will GCSB() on guest_exit, and host/hyp does not use GCS, there should be no GCS pending operation at the entry point. Am I missing something? Thanks! Leo
